MIDI recording question

not sure why it would say MAC - that's kind of odd.  I'd just wait until you get the keyboard and connect it and see if that works, if not, you may have to worry about lexicon drivers, but at this point, I'd just ignore it until it doesn't work.

yes, you'll need at least one MIDI cable.  if you're only recording MIDI and not sending MIDI back to your keyboard you'll only need 1 cable, but if you plan to do both, you'll need 2 MIDI cables.  IMPORTANT:  the INPUT on the KEYBOARD connects to the OUTPUT port of the Omega, and the OUTPUT port of the Omega connects to the KEYBOARD INPUT port.

set the input as OMNI unless you're trying to send more than 1 channel at a time is fine.

set the output channel whatever channel your keyboard is receiving MIDI on (usually most keyboards will default to channel 1, but that's not necessarily true, you have to check the keyboard manual).

5) NO - MIDI is DATA ONLY.  if you want the actual sound of the actual keyboard you will need to use the 2nd MIDI cable for the OUTPUT.  THEN set up audio cables from the keyboard back to input to the soundcard, then set up an audio track and arm it.  that way when you record the MIDI, you can then edit MIDI, then send the MIDI back to the keyboard, which will send the audio to the soundcard audio track and then record the audio from the keyboard.

but if you're using softsynths you don't need to do all that.  you just record the MIDI using softsynths and don't worry about the output from the computer back to the keyboard and the sound will be triggered in the softsynth instead of the keyboard.

6) MIDI is data only.  if you're only recording the MIDI then the quality of the keyboard will not make any difference at all.  if you're trying to record the actual sounds of the keyboard, that will be a different story.